Varnish Instead of Fiberglass?

Fiberglassing over plywood and one-off fiberglass methods. See: "Boatbuilding Methods", in the left-hand column of the Home page.

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uscga
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Varnish Instead of Fiberglass?

Postby uscga » Thu May 30, 2013 5:37 pm

I am just looking into building a boat and fiberglassing looks scary. Would it be okay to just varnish the hull with like ten coats initially and then reapply every year?

Thanks!

bige13
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Re: Varnish Instead of Fiberglass?

Postby bige13 » Thu May 30, 2013 7:24 pm

As well as sealing the wood to prevent wood rot the fiberglass ads a significant amount of strength. varnish give you more of a cosmetic look and not a strengthener. fiberglass is not a big deal. all you have to do is read the directions on you epoxy and do a test peace or two.

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jprice
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Re: Varnish Instead of Fiberglass?

Postby jprice » Fri May 31, 2013 7:23 am

It wouldn't take much to scrape through the varnish. Then you'd have exposed raw wood absorbing water. Fiberglass gives you a hard layer of protection that helps prevent all those bumps and scrapes from getting down to bare wood.

Can you build a boat without it? Sure. But if you're going to put all the time, effort and money into building one, then fiberglassing the exterior is a very worthwhile insurance policy.
It's really not that hard either. You're basically just brushing/rolling epoxy over a piece of cloth on your boat.

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Bill Edmundson
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Re: Varnish Instead of Fiberglass?

Postby Bill Edmundson » Fri May 31, 2013 7:48 am

Epoxy is also fairly forgiving (Mix in small batches.). It doesn't set-off like polyester resin. If you really screw-up, with a heat gun the whole mess can be pealed off.

Bill
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jamundsen
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Re: Varnish Instead of Fiberglass?

Postby jamundsen » Sat Jun 01, 2013 7:36 am

I too was nervous about the fiberglassing of the hull. In the end it turned out pretty easy to do.
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Re: Varnish Instead of Fiberglass?

Postby Brian » Thu Jan 21, 2016 6:57 pm

I've got my Monte Carlo bottom about ready to finish and flip (what a day THAT will be!). We have people here in Hawaii who are experts with fiberglass, so I have enlisted their advice. One of them says to glass the whole bottom from keel to sheer. The other wonders why bother with fiberglass? The no-glass guy (a real expert who has glassed a lot of wood boats and surfboards) says that 4 or even 6 oz cloth is not really much protection, subject to "starring" from little dents you wouldn't even notice on wood, and offers only un-needed additional strength on a 3/4" cold molded hull. I was thinking of glassing only from the keel to the waterline, and now I'm wondering, "Why glass at all?"

My bottom is 3/4" on the sides as well (vs 5/8" in the plans), laminated with structural epoxy, nails and screws. Every piece of wood is saturated with Smiths CPES. Every Mahogany seam is full of epoxy, and I'm pretty sure the glue contact with the plays good (wish I had done vacuum). The boat will only be in the water (CA fresh only - not for Hawaii) for short periods 2-3 times a summer, and never even on a buoy. With the CPES and several coats of polyurethane (plus bottom paint), it's hard to imagine water getting in behind the Mahogany, let alone the ply.

On the other hand, one never knows if the hull is going to develop seam cracks or other points where water can get in. But I'm still thinking, even if that were to happen, it would be during a day of boating, and then the boat is back on its trailer in the summer heat in very low humidity (Lake Tahoe is 6,200'). So any little water creeping in over several hours should dry out quickly. Plus, it should be easy to find and easy to fix, vs fiberglass.

I'm trying to find good logic for abandoning fiberglassing altogether (saving me a month to the flip). Any support for that, or would I be a fool not to do it?

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jamundsen
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Re: Varnish Instead of Fiberglass?

Postby jamundsen » Thu Jan 21, 2016 7:24 pm

Fiberglass it.
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Re: Varnish Instead of Fiberglass?

Postby Brian » Thu Jan 21, 2016 8:07 pm

OK.

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Dave Grason
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Re: Varnish Instead of Fiberglass?

Postby Dave Grason » Thu Jan 21, 2016 9:33 pm

Yeah, I think EVERYONE has been somewhat put off by the prospect of fiberglass. I know I certainly was. But really, it's very easy and straight forward. It's not rocket science at all.
Isn't it amazing!! The person that never has the fortitude to pursue his own dreams, will be the first to try and discourage you from pursuing yours.

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Re: Varnish Instead of Fiberglass?

Postby Brian » Thu Jan 21, 2016 9:42 pm

Actually, that's not the reason for asking at all. I have two VERY experienced guys to help me, and they are totally confident. I'm just questioning whether it's necessary. It's a question they posed to me, because one of them could see no benefit and the other said he could go either way.

That said, I think I will glass it, sheer to keel. One of the glass guys said one benefit he could see would be if a board had a tendency to expand, move around or open slightly at a seam, the glass might provide enough holding power to keep it in place. Both of them recommended 10 oz cloth, not the 4 oz provided by Glen-L. Nonetheless, I think I'll use the 4 oz, since it will be easier on the bends, over the chine, and have a better chance of coming out totally clear. Then I'll see if there are any objectionable imperfections, paint and a clear polyurethane final.

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Dave Grason
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Re: Varnish Instead of Fiberglass?

Postby Dave Grason » Thu Jan 21, 2016 10:38 pm

The 4 oz cloth is for covering a deck where the desired look is for the natural beauty of the wood to show well. It's a light weight cloth that gives abrasion protection and stabilization but it virtually disappears from sight when the epoxy is applied. It's a compromise between protection and appearance. Obviously, the 10 oz cloth will provide a higher level of protection but it would be more difficult to hide. The grain of the wood would appear cloudy and somewhat out of focus. I used the 10 oz on my Zip but it will be painted and so, I figured that using the heavier cloth was a better choice since it would be painted anyway. You may have to apply several coats of epoxy before the texture of the cloth is well hidden. I did. You don't really want to be sanding into the cloth as you prepare the surface for paint. Applying more coats is easy. Just have a new batch mixed up and be ready to start pouring and spreading when the previous coat is tacky. In order to determine the correct tackiness, lightly drag a cotton ball across the surface. It should pull just a very few hairs off the cotton ball and no more.


I haven't planked my deck yet and I will use the 4 oz cloth on it when I do.
Isn't it amazing!! The person that never has the fortitude to pursue his own dreams, will be the first to try and discourage you from pursuing yours.

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Re: Varnish Instead of Fiberglass?

Postby Brian » Fri Jan 22, 2016 1:04 am

I bought the "whole kit" from Glen-L with the plans, and they provide 4 oz. I might just go to 6 oz as a sort of compromise for the bottom. The guys I have helping me will make sure the cloth disappears. Both these guys have made some gorgeous stuff and you cannot see any trace of cloth.

Still some more skim coat and sanding to do to get both the painted and wood surfaces perfect. I'll be glad to put that sander away!

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vupilot
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Re: Varnish Instead of Fiberglass?

Postby vupilot » Sun Jan 24, 2016 7:58 pm

Fiberglass also helps a lot with the movement the wood makes just in everyday heating and cooling. As the wood heats and cools everyday in storage or on the water and expands and contracts your varnish can get little hairline cracks wherever two pieces of wood butt together. 4oz fiberglass on the deck and will keep that movement to a minimum and your finish will last much longer. As for the hull sides and bottom, just think about the first time you hit a chunk of driftwood or other piece of debris at 50mph. Your one friend is right, fiberglass doesn't really make the boat significantly stronger BUT the ABRASION resistance IS certainly significant as is the stability it adds to the expanding and contracting of the wood as Dave mentioned.

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Re: Varnish Instead of Fiberglass?

Postby Brian » Sun Jan 24, 2016 8:24 pm

Thanks, and that is the MAIN reason I will glass the whole thing. I've already noticed those little cracks from heating and cooling.

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Re: Varnish Instead of Fiberglass?

Postby Brian » Sun Jan 24, 2016 9:36 pm

I have another question. The Glen-L fiberglass instructions say to run the cloth lengthwise on either side of the keel. The guys I'm working with here want to go athwartships with it in sections of 50" (the width of the cloth), chine to chine. Does it matter either way?


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